Stereoscopic range indication



Sept. 9,1947. I

1 VERTICAL SWEEP 66 i-Au uruoel.

POSITION t CONTROL 5 I W. A. AYRES STEREOSCOPIC RANGE INDICATION Filed m 9, 1943 FIGS ,"qg'

SCANNER RECEIVER OSCILLATOR CONTROL PULSE GENERATOR TIME SWEEP STEREO CONTROL HORIZONTAL AMPLIFIER VERTlOAL AMPLIFIER :llllll lll lllll'l 2 Sheets-shat 2 AMPLITUDE 8- POSITION CONTROL s2- AMPLIFIER AMPLIFIER M5 AMPLIFIER AMPLIFIER.

n A a ns. sar57 swear GENERATOR |i mvsmoa 56 WA.AYRE$ OSCILLATOR ATTORNEY Patented Sept. 9, 1947 UNITED STATES PATENT OFFICE STEREOSCOPIC RANGE INDICATION Waldemar A. Ayres, Kew Gardens Hills, N. Y., assignor to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation of New York Application March 9, 1943, Serial No. 478,586

9 Claims. 1

The present invention relates generally tostereoscopic range finders and more particularly,

to stereoscopic distance determination in micro wave object detecting and locating systems.

Means for producing a three-dimensional picture of remote objects have been disclosed by the present inventor in his copending patent application Serial No. 458,109, titled Synthesized stereoscopic vision, filed September 12, 1942. In that application, the stereoscopic picture is synthesized from the positional data obtainable by a reflected pulse type of microwave object detecting and locating system employing a single electromagnetic energy collector, and is adapted to reveal the positional relationships of a plurality of objects in a realistic .and instinctively comprehensible manner.

It is often desirable, however, in such applications as aircraft interception and aircraft gun laying, to have an absolute range scale with which the relative distances of objects may be compared and to be able to determine accurately the range of an individual object without destroying the goniometric indication of the measured object and its positional relationship to other objects.

It is, therefore, the principal object of this invention to provide a stereoscopic range indication for use with microwave object detecting and locating systems which produce a three-dimensional picture of the area scanned.

Another object is to provide an absolute distance scale simultaneously observable in relation to all objects detected in a desired scanning area.

Yet another object lies in the provision of electronic means for stereoscopically determining the accurate range of an individual object while maintaining undisturbed an indication of the relative positions of all objects detected ina desired scanning area.

A further object is to superimpose on a threeduced by a cathode ray indicator a stereoscopic range scale which may be electronically posiscopic displacement as employed in the specification and claims.

Fig. 2 is a graph of the stereoscopic displace- 2 ment of an image on an indicator screen as a function of'the distance from the viewpoint to the corresponding object. x

Figs. 3A and 3B are oscillograms of time sweep waves corresponding to the stereoscopic displacemcnts curves of Fig. 2.

Fig. 4 is a stereoscopic drawing which illustrates some of the possible types of range indications and which may be observed in three-dimensional relief by means of an ordinary stereoscope.

- Fig. 5. is a block diagram of a simplified microwave object detecting and locating system em? playing an embodiment of the present invention.

Fig. 6 is a schematic wiring diagram of a pushpull output amplifier having two single-ended inputs.

Fig. 7 is a schematic wiring diagram of a gain and direct voltage level control.

Similar characters of reference are used in all of the above figures to indicate corresponding parts. In Fig. 5 arrows are provided to indicate the direction of control or energy flow.

The theory underlying the present invention may be more readily understood by reference to Figs. 1 and 2. In Fig. 1 objects symbolized by dots I, 2, and 3 lie at distances increasing in numerical orderfrom a viewpoint 4, For clarity and simplicity in illustration, all the objects are assumed. to be on the same line of sight 5. This line is broken at 6'to show that object 3 lies at an extremely great distance. Now assume a surface I at some distance from the viewpoint 4.- The points at which the lines of sight to objects pierce the surface I may be termed the goniometric positions of images of objects as represented on surface I. The goniometrically positioned images corresponding to objects I, 2, and 3 are coincident at a point 8. It is seen that all objects having the same hearing from a singular viewpoint possess images whose goniometric positions superim pose irrespective of the distance to the corresponding objects. 1

Assume now that viewpoint B is replaced by imaginary left and right viewpoints 9 and I0, respectively, separated by an effective interocular distance. Left and right rays passing through the objects pierce the surface I to form dual images, I, 2', and 3 for the left viewpoint 9, and I", 2", and 3" for the right viewpoint M. It is seen that images I and I" corresponding to object l lying in front of the surface 1 are displaced from the goniometric position 8 to the right and left, respectively, while images 2' and 2" corresponding to object 2 lying beyond surface I suffer a reverse displacement from the with the transmission ing on the surface would not be displaced from the goniometric position. 'Since object .3 is 8.57-

sumed extremely distant, leftand right rays to.

this object are substantially parallel to sighting line 5, and images 3' and 3 therefore, have sub- Y stantially the same separation a points 9 and ID, that is, the eflective interocular distance. The

lateral displacement of images from their goniometric positions .caused by the assumption-of goniometricposition 8, being to the left and right, as numerals. pips, lines, circles, etc., superimrespectively. Images corresponding to objects ly.-

posed on the stereoscopic indication 01' objects.

Fig. 4 illustrates some of these possible reference imaginary right and left viewpoints may be called stereoscopicdisplacement and evidently varies according to distance. Fig, 2 illustrates the general relationship between-stereoscopic displacement of from the viewpoint 4.

-; images and distance of the .corresponding'objects A stereoscopic indication of objects I, 2. and 3 r maybe achieved by providing an indicator screen Y having images thereon positioned similarly to thoseon surface 1 where images. I, 2', and iiare visible only to the left'eye of an observer while imagesl"; 2',', and 3" are perceivedyonly by .the'

observer's right eye. jIma es seen by the left .eye

are .paired in the observers 'brainwith comple- A mentary images seen by'the right'eye, and the d pth relation' l transmitter ll through a commutator I4. These fusion results in a perception of ships between the objects i. 2, and 3.

- "The present inventor has. disclosed in the above-mentioned copending application Serial No. 458,109,' that suchha stereoscopic indication .may be produced synthetically by goniometricallypositioning images according-to the bearings of objects as located by a single scanningradiator,

and stereoscopically displacing these images according to the distance to .the respective objects. The presentinventoniurther revealed that only one viewpoint is thus'necessary if the distance toall objects is determinablea v The reflected-pulse type or microwave'object detecting and locating system is particularly Q I adapted to-provide three-dimensional pictures oi v mentarily.

markings as they might appear on a cathode ray tube screen. The left circle is the indication intended only for the left eye while the right circle isthe indication intended only for the right are. some typical means for producingthis general type of indication'are now discussed.

Referring now to Fig. 5; one embodiment oi the present invention is disclosed as employed in a reflected-pulse type of microwave system. In the system illustrated a control oscillator I i of any substantially sinusoidal oscillations ted to it into pulses of any desired shape, magnitude, and duration, having a repetition, rate equal to the frequency of oscillator ii. This device employs well-known clipping, differentiating, and other a suitable wave shaping circuits in a conventional manner and consequently seems 'to require no further explanation.

Sharp trigger pulses are supplied to amuse trigger. pulses cause an ultra high frequency oscillatersuch as a magnetron to be biased on mo- Transmitter i3 isthus made to produce, extremely short pulses oi perhaps Jone micro-second duration. These pulses of carrier frequency are'fed to a scanner mechanism I5.

shown in -copending application Serial No. 438,388,

-fi1ed April 10, 1942, in the .The scanner" may be oi the general type names of L. A. May- -.bard uk'et al although the invention is in no way limited to any particularmodeof scanning. Such the area scanned because the-distance to detected objects is proportional tothe transit time between I i the transmission of a pulse and thereception of the pulse, after j reflection'from the objects.v A

time sweep wave may readily be synchronized of pulses to provide'an instantaneous amplitude which is a function of distance. fIhe scanningagerit of an indicator such [as the electron beam of a cathode ray tube may be deflected in proportiongto. this instantaneous amplitude with 'the result that the-stereoscopic displacement of j the luminous image varies with distance in accordancewith the characteristics of v the time sweep wave.

Figs. 3A and '3B illustrate the time sweep waves correspondi-ng'to the stereoscopic displacement curvesv of Fig; 2. These curvesrepresent the realistic relationship between displacement and distance but may often'fbe adequately approximated by an exponential or linear shape over the desired. distance limits. Any other/wave shape may be employed to suit the particular need. The amplitude of the; time sweep wave determines the stereoscopic contrast between nearest a,scanning device is adapted to scan a p'redeterminedsolid angle up to and including a complete hemisphere by means of a spiral conical motion of a sharply directive radiaritv energy beam. This motion is provided by-rapidly spinninga radiator. indicated at ll about one axis while slowlynodding the radiating system about a second axis perpendicular to and rotating with the flrsfiiiris'. The transmitter pulses are-emitted in a narrow club-shaped beam from the radiator I8, and the .r requencyPfthe control oscillator II" is chosen sufllciently high to insure that all objects within ,the field- 01 view are irradiatedby at least one pulse during the scanning cycle. Radiator I 8- serves also to receive energy reflected from ob-.

jects during intervals between successive transmission periods andto supply the reflected enersy' to a receiver I1.'-

The'receive'r n and the transmitter I3 m 4 electricallyisolated by-meansof well known gas-- filled resonators incorporated in the connections to the radiator l8.

transmitted and received pulses and provide an vents appreciable transfer of generated power di- .rectly to the recelver'but also eliminates loss of and furthest.images-whilethe average value of direct component determines the apparent distance to the indicator surface. 'It' is preferable i that the time sweeps employed for the right and left eye indications be equal and opposite to'avoid I distortion of the apparent bearings of objects.

According to the present invention range scales or lndices may be provided; in such-va iedf r s received energy in the transmitter. Examples quency devices, and flledNovember-ZO, 1942.

The receiver .1 'l-amplifies and detects the receivedpulses in the usual manner and applies them through a commutator 18 to a control grid '19 of a cathode ray indicator 2|. 'To further These resonators are responsive to thev difierence in power between insure that no transmitted pulses directly affeet the receiver II, blanking pulses may be furnished from the pulse generator I2 over a line- 22 in order to bias the receiver to insensitivity for the duration of each transmitted pulse. The detected pulses on the grid I9 turn on the elec-' tron beam of the indicator 2| after a delay behind their respective transmitted pulses according to the time required for radiant energy to travel to the point of reflection and return. The reflected energ thus produces images on the face 82 of the indicator 2| which correspond to irradiated objects. I

The images ofdetected objects are goniometrically position on indicator face 82 by means of a vertical sweep circuit 23 and a horizontal sweep circuit 24, mechanically connected to the scanner mechanism I5 and adapted to convert the scanning motion of the radiant beam into corresponding electron beam-deflecting potentials for the cathode ray indicator 2|. Circuits 23 and 24 connect through commutators 25 and 26, respectively, to vertical and horizontal deflection amplifiers 21 and 28, respectively.

The amplifiers 21 and 28 may conveniently be of the type shown in Fig. 6 having a. push-pull output and two single-ended inputs. Here two identical tubes 29 and 3| have in common a high resistance cathode load 32 maintained at a large negative potential. A signal applied to either grid 33 or 34 appears across plate resistors 35 and 36 with opposite polarity and substantially equal magnitude. Cathode ray deflecting electrodes directly coupled to leads 39 and 40 displace the electron beam according to the sum of the impressed voltages whether alternating or direct. The operating potential on the tubes29 and 3| being the same on each deflecting electrode causes no beam deflection.

The images of detected objects are stereoscopically displaced from their goniometric positions on the indicator face 82 by the employment of a time sweep circuit 31 and associated stereo control circuit 38 acting through a commutator 53 to supply the horizontal deflection amplifier 28 with stereoscopic displacement waves. The pulse generator I2 triggers the time sweep circuit 37 coincident with the transmission of radiant pulses from radiator I6. The instantaneous amplitude of the sweep voltage may be any desired function of time such as a. substantially hyperbolic, exponential, or linear Wave according to' the desired stereoscopic displacement wave, Since sweep circuits are well known, no detailed discussion is necessary. The output wave of the sweep circuit 31 is fed in push-pull to the stereo control circuit 38 which ma comprise two cathode-follower stages each similar to the one illustrated in Fig. '7.

The cathode-follower stage shown in Fig. '7 comprises a tube 39 attached to a cathode load consisting of a voltage divider 4| in series with a high fixed resistor 42,'.the combinationbeing connected to a source several hundred volts negative with-respect to ground. The midpoint of the voltage divider 4| is approximately at ground potential. An adjustable tap 4I is electrically connected to an output lead 48 and mechanically adjusted by 'a direct voltage level control knob 49. A voltage divider 43 is connected between an input lead 45 and ground. An adjustable tap 44 connects to the control grid of tube quarter revolution of the commutators.

5| to allow simultaneous adjustment of the amplitudes 0f the stereoscopic displacement waves passing through its two cathode-follower stages. Control circuit 38 is further provided with a knob 52 to facilitate alteration of the direct voltage level of these waves by preferably equal and opposite amounts. One stage of the circuit 38 has an output lead I26 upon which its stereoscopic displacement wave is impressed, while the parallel stage of the circuit 38 has an output lead I21 to which the substantially mirror image of the above wave is supplied. Leads I26 and I2! are alternately connected through the commutator 53 to the second input of the horizontal deflection amplifier 28 in whose output the stereoscopic dlsplacementwaves are algebraically added to the goniometric potential from sweep circuit 24.

Images therefore appear on the indicator face 82 suitably placed for either right or left eye indication according to whether lead I26 or I21 supplies the stereoscopic displacement wave. These indications are repeated at a rate sufficiently high to avoid flicker, and viewing means are provided to enable an observer at a viewpoint I20 to see these indications as a unified threedimensional picture.

The following viewing means may be employed to permit the right and left eyes of the observer to see only the indications intended for the respective eyes, the left eye indication being obscured from the right eye and vice versa. A motor I2 drives the scanner mechanism I5 and rotates commutators 25, I8, I4, 53; and 26 through gearing I3. An intermittent motion mechanism 83 such as a Geneva movement, is driven synchronously with the commutators by means of gearing I28 and I29. The mechanism 83 has a driving pinion I9 which engages a ring gear 8| supported parallel and concentric with the indicator face 82 by suitable bearings (not shown). The ring gear 8| provides a supporting frame for a polarizing screen held before the face 82. This screen may be made of a commercially available transparent sheet adapted to plane polarize the light it transmits. The oscilloscopic picture as viewed through this screen is therefore optically polarized in a plane corresponding to the angle of rotation of this screen about the line of sight.

The intermittent motion mechanism 83 is adapted to rotate or oscillate this screen by means of the gearing I9, 8| in progression after each The plane of polarization may, for example, be vertical and horizontal, successively, for the major portion of the time and may pass through intermediate angles very rapidly. If the face 82 is observed from viewpoint through polarizing eye glasses, indicated at I2I, the right and left lens transmitting only vertical and horizontal polarizing light, respectively, the observers right and left eyes respond only to those indications.

intended for these eyes. The dual images corresponding to each object are fused in the brain of the observer and provide a three-dimensional picture. It is (to be understood that other viewing means, such as those shown in above-mentioned copending application Serial No. 458,109, may be alternatively employed.

In the embodiment of Fig. 5, the range indices exist as patterns formed on targets I4 and I5 in picture source cathode ray tubes 54 and 55, respectively. These patterns are analyzed in terms of video signals and scanning potentials and are sweep generator 58.

then reproduced on the indicator face 82. Range indices may also exist as a pattern formed in a single picture source tube or may be generated without aid of such tubes as more specifically disclosed and claimed in copending patent application Serial No. 478,583 titled Synthesized stereoscopic-range indication filed March 9, 1943, in For the presentthe name of E. C. Streeter, Jr. purposes the following means are provided.

An oscillator 56 supplies a carrier wave to 54 and. having vertical amplitude al'idright-lei't position adjustment knobs 65 and 68, respectively.

Amplifiers 62 and I6 are connected to vertical and horizontal deflection plates, respectively, inv the picture source cathode ray'tube 54 while amplifiers 11 and BI are connected to corresponding deflection plates in the tube 55 similar to device 54. The quadrature phase relationship between the deflection potentials .causes the electron beams in tubes 54 and-55 to scan metal targets 14 and 15, respectively, with a substantially spiral motion. 'It is to be understood that the use of spiral scanning is merely illustrative and that rectangular or other types of scanning may be employed with equal fitness. The targets 14 and 75 .are preferably made of metalhaving a high secondary emission ratio such as aluminum. foil with a natural oxide coating. The desired left and right range patterns may be printed on the surface of targets 14 and 15, respectively, in carto the scanner mechanism i5 such thatthis switching action occurs at the end of each scanningperiod of the radiator l8. During range indication, vertical and horizontal sweep circuits 23 and 24, respectively, stereo control circuit 38 and receiver 11 are disconnected from the indicator 2i while transmitter i3 is deprived of trigger pulses from generator i2. The momentary position of the commutators illustrated in Fig. 5

corresponds to about mid-period of the right-eye.

indication of objects.

The placement of the range-patterns on the face 82 of the indicator 21 may be adjusted as desired by up-down and right-left control knobs 65 and 68. The size of the range indices may be adjusted by vertical and horizontal amplitude controls 55 and 61, respectively, while the usual position adjustment in horizontal deflection amplifier'" is connected to a knob 18 to provide for variation of the apparent plane of the indicator face 82 during periodsof range reproduction. Al-

teration of the horizontal sizeof the range indices naturally causes a change in the lateral spacing between right and left pairs of images.- This is equivalent to an alteration in th stereoscopic contrast of the range indices. Amplitude and positioning knobs 5i and 52 of the stereo control 38 are suitably adjustedso that the stereoscopic contrast and the apparent plane of the indicator face 82 are the same duringthe periods of object indicationas during the periods of range indication. 5

Sirlcetthere is wide variation. in the types of mechanical and electronic scanning encountered in object locatorsystems and in the particular range indication requirements of these systems,

many changes or rearrangements could be made in the above-construction to suit specific needs and many apparently'widely difierent embodiments .of this invention could be 'made without departing from thescope thereof, itbeing intended that bon ink or other material having a. secondary v emission ratio appreciably different from the natural oxide;

As the targets .14 and 15 are scanned, variations in the secondary emission current from the range patterns produce video signals correspondingto the indices to be reproduced. Since the difierence in magnitudes of secondary emission determines the video current, it is possible to' develop a greater signal than would be provided by'the use of the primary current of the electron beams alone. The signal outputs of tubes 54 and 55 are supplied to-video amplifiers 69 and, respectively. The signals amplified by the devices '69 and are fed to contacts 8 and I22 of grid commutator IS. The outputsof control circuits 63 and 64 supply the vertical and horizontal components, respectively, of the sweep produced by circuits 56, 51, 58, and 59 to the contacts H1 and 25 and 26, respectively. I

The commutators i8, 25, and 26 permit the placement of the range indices, as thus analyzed 1 IQ of vertical and horizontal sweep commutators in terms of video signals and scanning potentials,

upon the indicator face 82. The commutators are represented as having insulating portions in black and conducting segments in white.

The commutators supply right and left eye indications all matter contained'in the'above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense. I r

- What is claimed is:

1.'A radio receiving. system comprising a re-,

ceiver'of periodic pulse signals, cathode ray indicating means provided with-a viewing screen, means for forming dual images from said, pulse signals laterally separated-on said viewing screen according-to a periodic function of time, means for generating stereoscopic reference signals, means for forming dual indices from said reference signals laterally separated on said viewing screen, and stereoscopic viewing means for observing the apparent depth relationship between said images and said indices.

2.'In a radio loca'tor system wherein gonion'retrically located dual. images are formed on a viewing screen in response to reflections from irr radiated objectasaid images being separated asa. function of range to provide stereoscopic effects, the combination comprising means forscanning targets with electronbeams, means for generating video signals through difilerentialreaction of por- I tions of said targets to said beams, means for of objects and rightand left, 'eye indications of range indices in repeated sequence to the indicator 2|. Each indication occupies substantially a 'quarter revolution of the commutators. The commutators have a gearing ratio with respect varying the intensity of a reproducing beam in accordance withsaid video signals, means for defleeting said reproducing'beam in accordance with said scanning. and means for modifying said de .fiection to produce stereoscopic'efiects. 3. 'In a radio locator system wherein goniometrically'located dual images are formed on a viewing screen in response to reflections from irradiated objects, said images being separated as a function of range to provide stereoscopic effects, the combination comprising electron beam tubes, a target in each of said tubes having a surface for receiving the electron beam, portions of said surface being provided with distance indices receptive to said beam differently from the remainder of said surface, means generating sweep waves for deflecting said beams over said targets, means for amplifying video signals resulting from the-difi'erent receptivity of said surface portions, and means responsive to said signals for reproducing said distance indices on said viewing screen spaced in accordance with said sweep waves.

4. Radio object detecting apparatus comprising transmitting means for irradiating an object periodically with electromagnetic energy pulses, receiving means for deriving signals from a portion of said energy pulses reflected from said object, indicator means for forming dual images from said signals, means for stereoscopically separating said dual images as a function of distance to said object, electron beam tubes, a target in each of said tubes having a surface for receiving the electron beam, portions of said surface being provided with distance indices receptive to said beam differently from the remainder of said surface, means generating sweep waves for deflecting said beams over said targets, means amplifying video signals resulting from the different receptivity of having a. surface for receiving the electron beam,

portions of said surface being provided with distance indices receptive to said beam differently from the remainder of said surface, means generating sweep waves for deflecting said beams over said targets, means for amplifying video signals resulting from the different receptivity of said surface portions, means responsive to said signals for reproducing said distance indices on said viewing screen spaced in accordance with said sweep waves, and control means for altering the separation of said indices on said screen.

6. In a radio locator system providing a threedimensional representation of a scanned area, the combination comprising cathode ray indicating means provided with a viewing screen, elec-- tron beam tubes, a tar et in each of said tubes having a surface for receiving the electron beam, portions of said surface being provided with distance indices receptive to said beam differently from the remainder of said surface, means generating sweep waves for deflecting said beams over said targets, means for amplifying video signals resulting from the different receptivity of said surface portions, means responsive to said signals for reproducing said distance indices on said viewing screen spaced in accordance with said sweep waves, and a variable gain control for altering the magnitude of said indices on said screen relative to said three-dimensional representation.

7. In a radio locator system providing a threedimensional representation of a scanned area, the combination comprising cathode ray indicating means provided with a viewing screen, electron beam tubes, a target in each of said tubes having a surface for receiving the electron beam, portions of said surface being provided with distance indices receptive to said beam differently from the remainder of said surface, means generating sweep waves for deflecting said beams over said targets, means for amplifying video signals resulting from the different receptivity of said surface portions, means responsive to said signals for reproducing said distance indices on said viewing screen spaced in accordance with said sweep waves, and positional control means for adjusting the position of said indices on said screen relative to said three-dimensional representation.

8. Stereoscopic apparatus comprising a source of periodic pulse signals, cathode ray indicating means providing a field of view and supplied by said source for forming dual images from said pulse signals, means producing a time sweep having the same periodicity as said pulse signals for laterally separating respective portions of said images in said field of view according to a periodic function ,of time, means for generating reference signals, means for forming stereoscopically separated dual indices in said field of view in response to said reference signals, and stereoscopic viewing means for observing the apparent depth relationship between said images and said indices.

9. A radio receiving system comprising a receiver of periodic signals, cathode ray indicating means providing a, field of view and supplied by said source for forming dual images from said pulse signals, means producing a time sweep having the same periodicity as said pulse signals for laterally separating respective portions of said images in said field of view according to a periodic function of time, means for generating reference signals, means for forming stereoscopically separated dual indices in said field of view in response to said reference signals, and stereoscopic viewing means for observing the apparent depth relationship between said images and said indices.

' WALDEMAR. A. AYRES.

REFERENCES crrnn The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number 1 2,121,359 

